Ventilating insert for abrasive tools

ABSTRACT

A ventilating insert for the substantially coaxial fixing of abrasive tools, such as deburring wheels, cutting wheels, fiber discs, Scotch-Brite® having an abrasive disk-like element, to the free end of a rotating shaft of a grinder, comprising at least one threaded ring for coupling to the free end of the rotating shaft, an annular portion of which is jointly associated with the disk-shaped element, the threaded ring comprising a central threaded hole and being designed to be arranged substantially coaxially with the disk-shaped element and able to be associated with corresponding threaded elements provided on the free end of the rotating shaft. 
     The ventilating insert comprises deflectors for at least one fluid for cooling the disk-like element which are associated with the threaded ring for propelling radially the cooling fluid from the central to the peripheral region of the disk-like element during the rotation thereof.

The present invention relates to a ventilating insert for abrasive tools designed to be installed on sanding machines.

BACKGROUND OF THE INVENTION

There are various types of abrasive tools designed to be installed on portable machines. The most widespread among them are: abrasive deburring wheels and abrasive cutting discs with resinoid binder, for example of the high-speed type to be used on portable sanding machines with diameters that vary from 100 mm to 230 mm, lamellar discs, Scotch-Brite® discs, fiber discs, etcetera.

All these tools have in common that they are installed on a sanding machine or polishing machine and turned to apply their abrasive action or cutting action.

An abrasive deburring wheel, for example, consists of a disk provided by a mixture of abrasive grains, binding resins and fillers, which is mounted on an adapted grinder, commonly known as a sanding machine, is rotated about its own axis and then placed in contact with the part to be ground, or vice versa.

In order to be able to mount the grinding wheel, sanding machines usually have a rotating shaft that is provided with a centering system, an abutment shoulder, a thread at the free end and two fastening flanges.

One of these two flanges is fitted on the sanding machine shaft and engages the shoulder and the centering system thereof. The other flange is instead provided with a central threaded hole and is screwed onto the shaft. The grinding wheel, in working conditions, is interposed between these two flanges and is firmly fixed thereto by screwing the threaded flange on the sanding machine shaft with a certain strength. Finally, the grinding wheel is kept concentric with the shaft by means of two centering protrusions formed on the faces of the flanges that are in direct contact with the grinding wheel. These protrusions enter a few millimeters into the central hole of the grinding wheel and ensure its perfect centering.

Deburring wheels can have various cross-sectional shapes which are specified by the EN12413 standard; the most common ones are the flat one and the one with depressed center, but there are also tapered ones or saucer-shaped ones. All of them, anyway, are mounted on sanding machines in a manner substantially similar to the one described above.

Abrasive grinding wheels of the flat or depressed-center disc-like type are known and described in detail in Italian patent no. 1,361,563 and comprise a disk-like abrasive and/or cutting element that can be associated coaxially with the free end of the rotating shaft of a grinder and is provided with a substantially central through hole, with a first face which can be positioned, in the mounting configuration, so that it substantially faces the grinder and is in contact with a supporting flange of the machine itself, and with a second face which lies opposite to the first one where a threaded ring for coupling to the free end of the rotating is jointly connected to the substantially central portion of the second face.

These abrasive deburring wheels are substantially constituted by an abrasive mix reinforced by reinforcements constituted by one or more nets made of fabric, by one or two optional annular elements made of metal or plastic material, commonly known as washers or rings, which delimit the hole for the coupling of the grinding wheel to the pivot of the grinder, and by an optional paper label, which adheres to one of the two faces of the grinding wheel (usually the convex one).

The abrasive mix is generally made of grains of abrasive material (silicon carbide, corundum, zirconium-modified corundum, and others) of predefined particle size (usually measured in meshes), which are mixed with resins and some additives. The resins are generally phenolic-based, in liquid and/or in powder form. Optionally, they can be modified with rubbers, epoxy resins and/or others, or with organic and/or vegetable or synthetic compounds.

The purpose of the reinforcement nets is to reinforce the structure of the grinding wheel and to allow its use at high rotation rates in complete safety. The high rotation rate is desired because the abrasive action is faster and work is performed more rapidly. However, high speeds involve high centrifugal forces and high tensions inside the body of the grinding wheel. In order to be able to withstand these high tensions, one therefore uses these reinforcement nets made of materials with high breaking strength. Generally, these nets are woven with glass fiber yarns, but it is also possible to use other types of high-strength fibers such as carbon fiber, Kevlar® or others; these nets, before being used in grinding wheels, are usually impregnated with resin, normally of the same type as the one used in the abrasive mix. The purpose of this operation is to achieve better adhesion between the net yarn and the abrasive mix itself, thus increasing the strength of the manufactured article. Finally, the nets are die-cut so as to obtain a shape (usually a round one) that is convenient for placement inside the grinding wheel.

The labels are usually made of paper but also of tin foil or other synthetic material, have an annular shape and bear the identification and informational data of the grinding wheel.

These grinding wheels of the known type, however, are not free from drawbacks, including the fact that during the deburring operation the friction between such grinding wheel and the workpiece generates a considerable amount of heat, which leads to an overheating of both the workpiece and the grinding wheel.

This overheating can reach such high temperatures that the resin of which the grinding wheel itself is composed breaks down. The resin thus loses its strength and causes the release of the abrasive grains and thus the wear of such grinding wheel. Moreover, this overheating can be harmful also for the workpiece, because it causes damaging effects of various types, such as:

burns and pitting with consequent bluish coloring of the surface of the metal piece, a phenomenon that is particularly unwanted for pieces made of stainless steel where visual appearance also is particularly important;

burns in wood or plastic materials;

drip melting in low-melting metals or in plastics;

modification of the crystalline structure of the metal in the case of self-hardening steels;

modification of physical and chemical characteristics in general for all materials that poorly tolerate high temperatures.

All of the above statements apply also in the case of lamellar discs, fiber discs, Scotch-Brite® discs or other abrasive tools.

Lamellar discs, for example, are composed of a circular supporting plate onto which flaps of abrasive cloth are glued. Abrasive cloth is a fabric (usually made of cotton or polyester) on which a thin layer of grains of abrasive material is fixed. The grains are fixed by spraying the fabric with resin, spreading the abrasive grains over it and finally polymerizing the resin. The flaps are obtained from the abrasive cloth by cutting strips of suitable width and finally cutting the individual flaps from the strips. Each flap rests on the supporting plate (already covered with glue or resin) so as to form an annular pack of flaps.

During use of the lamellar disc, as occurs for abrasive grinding wheels, a large amount of heat is produced and the temperature of the flaps and of the workpiece increases rapidly. At high temperatures the cotton (or synthetic fiber) of the abrasive cloth burns or melts, and the resin that holds the abrasive grains breaks down. All this entails wear of the abrasive material of the lamellar disc.

Moreover, the workpiece is affected by the same drawbacks caused by the heat which are described above for abrasive grinding wheels.

Fiber discs are simply pieces of abrasive cloth (sometimes paper) made in a manner similar to cloth for lamellar discs but die-cut to a circular shape.

The fiber disc is fixed to a supporting plate (which in turn is fixed to the rotating shaft of the sanding machine) mainly in two ways:

-   a. The abrasive cloth on the face opposite to the abrasive part has     a fabric made of Velcro® and the supporting plate has the     corresponding component for the Velcro®. The cloth is thus simply     held to the plate by the effect of the Velcro®. -   b. The center of the fiber disc has a hole that allows the passage     of the sanding machine shaft. A threaded flange screwed to said     shaft fixes the fiber disc to the back support.

In both cases, when the fiber disc is put to work it generates heat that breaks down the resin of the abrasive cloth, releasing the abrasive grains and causing wear of said fiber disc.

Scotch-Brite® discs are composed of a disc of abrasive material and a supporting plate. The supporting plate is generally made of fiberboard or plastic. The disc of abrasive material is instead composed of Scotch-Brite®, i.e., a material composed of nylon filaments in the matrix of which small abrasive grains are embedded.

Scotch-Brite® is produced by dropping onto a surface melted nylon filaments mixed with abrasive grains according to a random arrangement.

When the filament touches the surface it is already nearly solid and keeps the shape of a filament. Deposition continues until the desired thickness of the fabric is obtained and the finished product is therefore a lamina of filaments arranged in a random and disorderly manner.

This layer thus obtained is then die-cut and used for various applications. In the case of interest of the present description, the flap of Scotch-Brite® is die-cut so as to have a circular shape and is glued to the supporting plate.

The plate with Scotch-Brite® is perforated at the center and is mounted on sanding machines like an abrasive grinding wheel by fixing it between the two flanges, i.e., the abutment flange and the threaded fastening flange.

In this case also, when the tool made of Scotch-Brite® is working, the heat that is developed can reach the point of melting the nylon of which is composed, causing the release of abrasive grains without said grains having worked.

Scotch-Brite® tools must even be used at lower peripheral speeds than abrasive grinding wheels; otherwise the generated heat would be too high and the nylon would melt immediately.

As is apparent, in all the cases described above the heat generated by the abrasive action causes a more or less quick wear of the tool and harmful overheating of the material that is being worked.

SUMMARY OF THE INVENTION

The aim of the present invention is to eliminate the drawbacks noted above of the background art, by devising a ventilating insert that makes it possible to reduce the consumption of abrasive material, thus increasing its performance and average life.

Within this aim, an object of the invention is to allow the working of pieces without damaging their finish and their aesthetic appearance or altering their physical and chemical characteristics.

Another object of the present invention is to provide a structure that is simple, relatively easy to provide in practice, safe to use, effective in operation, as well as relatively inexpensive.

This aim and these and other objects which will become better apparent hereinafter are achieved by the present ventilating insert for the substantially coaxial fixing of abrasive tools, such as deburring wheels, cutting wheels, fiber discs, Scotch-Brite® discs or tools that otherwise can be related to an abrasive disk-like element, to the free end of a rotating shaft of a grinder, comprising:

-   at least one threaded ring for coupling to said free end of said     rotating shaft, an annular portion of which is jointly associated     with said disk-like element, said threaded ring comprising a central     threaded hole and being designed to be arranged substantially     coaxially with said disk-like element and able to associated with     corresponding threaded means provided on said free end of said     rotating shaft, -   characterized in that it comprises means for deflecting at least one     fluid for cooling said disk-like element which are associated with     said threaded ring for propelling radially said cooling fluid from     the central region to the peripheral region of said disk-like     element during the rotation thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a ventilating insert, illustrated by way of non-limiting example in the accompanying drawings, wherein:

FIG. 1 is a sectional side view of a detail of an abrasive grinding wheel, according to the invention;

FIG. 2 a is a plan view of the threaded ventilating insert of the grinding wheel of FIG. 1 in the variation with curved vanes;

FIG. 2 b is a plan view of the threaded ventilating insert of the grinding wheel of FIG. 1 in the variation with straight vanes;

FIG. 3 is a sectional side view of a detail of an alternative embodiment of a grinding wheel with ventilating insert, according to the invention;

FIG. 4 is a plan view of the threaded ventilating insert of the grinding wheel of FIG. 3;

FIGS. 5, 6 and 7 are sectional side views of further alternative embodiments of a ventilating insert according to the invention, which can be assembled at will on many conventional abrasive grinding wheels;

FIG. 8 is a sectional side view of a further alternative embodiment of a ventilating insert according to the invention;

FIG. 9 is a sectional view showing only the ventilating insert of FIG. 8;

FIG. 10 is a sectional side view of a further alternative embodiment of a ventilating insert according to the invention;

FIG. 11 is a sectional side view showing only the ventilating insert of FIG. 10;

FIGS. 12 a and 12 b are respectively a sectional side view and a plan view of a further alternative embodiment of a ventilating insert, according to the invention;

FIGS. 13 a and 13 b are respectively a sectional side view and a plan view of a preferred embodiment of a ventilating insert, according to the invention;

FIGS. 14 a and 14 b are views of two respective alternative embodiments of flat grinding wheels with a ventilating insert, according to the invention, in the configuration for fastening onto the rotating shaft of a sanding machine;

FIG. 15 is a sectional side view of a further alternative embodiment of a grinding wheel with ventilating insert, according to the invention;

FIGS. 16 a and 16 b are respectively a lateral elevation view and an axonometric view of a further embodiment of a ventilating insert with inclined vanes, according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the figures, a ventilating insert for the substantially coaxial fixing of abrasive tools, such as deburring wheels—generally designated by the reference numeral 1 in the drawings—, cutting wheels, fiber discs, Scotch-Brite® discs or tools that can otherwise be related to a disk-like element 2 of the abrasive type, can be connected to the free end of a rotating shaft of a grinder.

In particular, in the examples shown in the figures, reference is made to a depressed-center or flat abrasive grinding wheel 1, provided with a ventilating insert, but said ventilating insert might also be associated for the axial fixing of fiber discs, Scotch-Brite® discs or the like.

The grinding wheel 1 comprises an abrasive disk-like element 2 for deburring or cutting, which can be associated, in a substantially coaxial manner, with the free end 3 of a rotating shaft 4 of a sanding machine.

The disk-like element 2 is provided with at least one substantially central through hole 5, a first face 6, which can be placed (in the assembly configuration) so that it substantially faces the machine and is in contact with a supporting flange 7 of the machine itself.

Moreover, the disk-like element 2 is provided with a second face 8, which lies opposite the first face 6 and defines the active face of such grinding wheel (if it is a deburring wheel).

The ventilating insert comprises at least one threaded ring 9 for attachment to the free end 3 of the rotating shaft 4, an annular portion 10 of which is jointly associated with the disk-like element 2, and particularly in the case of the grinding wheel 1 with the substantially central portion 11 of the second face 8.

The threaded ring 9 comprises a central threaded hole 12, which is substantially coaxial to the disk-like element 2 and can be coupled to corresponding threaded means 13 provided on the free end 3 of the rotating shaft itself.

In particular, for the purposes of the present invention, the ventilating insert comprises means for deflecting at least one fluid for cooling the disk-like element 2, which are associated with the threaded ring 9 and propel radially the cooling fluid from the central region to the peripheral region of the disk-like element 2 during the rotation of the abrasive grinding wheel 1.

The cooling fluid is generally air, which is aspirated by the deflecting means during the rotation of the grinding wheel 1 in a direction that is substantially parallel to the axis of rotation of said grinding wheel, and is propelled in a radial direction by the same deflecting means.

Advantageously, the deflecting means comprise a plurality of vanes 14 that extend substantially radially with respect to the threaded ring 9 and diverge with respect to each other.

At least one first end 14 a of the vanes 14 is jointly associated with the threaded ring 9.

In the embodiments shown in FIGS. 1, 2 a and 2 b, the vanes 14 extend radially from the central threaded hole 12 to the outer perimetric rim 15 of the threaded ring 9 and are jointly connected, at the part directed toward the grinding wheel, to said threaded ring along the entire longitudinal extension.

However, the second end 14 b of each one of the vanes 14 might be substantially cantilevered, as shown in FIGS. 3 to 16, with respect to the threaded ring 9.

Such vanes, in this embodiment, protrude outward from such threaded ring so as to be substantially cantilevered on the disk-like element 2, for example extending beyond the outer perimetric rim 15 of such threaded ring.

This configuration is particularly visible in a preferred embodiment of the ventilating insert shown in FIGS. 13 a and 13 b, in which the vanes 14 protrude radially and externally with respect to the threaded ring 9, which has a substantially cylindrical shape.

Each one of the vanes 14 can comprise a substantially curved C-shaped or spiral-shaped longitudinal extension that defines a deflector for the flow of the cooling fluid, for example, of the type of a centrifugal fan or the like.

The threaded ring 9 is, for example, applied to the disk-like element 2 by interposition of a layer of adhesive material and/or by mechanical interference between a cylindrical portion 16 of the threaded ring 9 and the through hole 5. The threaded ring 9 can in any case be uncoupled from the disk-like element 2 and coupled thereto only at the time of installation of the element 2 on the shaft of the sanding machine simply by screwing it thereon.

This, in any case, prevents the threaded ring 9 from separating from the disk-like element 2 during handling, whereas during use the mechanical transmission of the motion and torque from the rotating shaft 4 to the grinding wheel 1 is ensured by the fastening of the grinding wheel against the supporting flange 7 of the rotating shaft 4.

This threaded connection allows the self-locking coupling between said grinding wheel and said rotating shaft, without thereby requiring lock nuts or similar devices.

In particular, as is known, the thread of the threaded ring 9 is such that, during the rotation of the rotating shaft 4, the torques acting on the grinding wheel 1 tend to turn the grinding wheel in the direction for screwing the threaded ring 9 on the rotating shaft 4.

The threaded ring 9, in one embodiment, comprises a substantially cup-shaped portion, whose concavity is directed toward the second face 8 of the disk-like element 2.

The cup-shaped portion surrounds the central threaded hole 12 and is arranged opposite the annular portion 10.

The vanes 14, advantageously, are defined at said substantially cup-shaped portion and are such as to protrude from the bottom thereof.

Advantageously, the vanes 14 have a height that is substantially equal to the depth of the cup-shaped portion of said threaded ring and/or the height of the cylindrical portion 16.

The vanes 14, moreover, in the region that is proximal to the central threaded hole, have mutual coupling surfaces for the optimization, in terms of fluid-dynamics, of the centrifugal thrust of the cooling fluid.

In a preferred embodiment, illustrated in FIGS. 13 a and 13 b, the vanes have a substantially straight shape and extend radially so as of protrude from the threaded ring 9; between each contiguous pair of vanes 14, provided in a cantilevered manner with respect to the threaded ring 9, the connecting surface between them (provided on the threaded ring itself) has a substantially frustum-shaped generatrix with a longitudinal axis that is substantially inclined with respect to the rotation axis of said threaded ring, the shell of which extends obliquely, forming a diverging channel along the entire thickness of said threaded ring.

This refinement allows an increase in the surface (also in the central region of the threaded ring 9) that is active in propelling the cooling fluid of each vane 14 and thus makes it possible to improve the ventilating effect imparted by the rotation of such threaded ring.

With this solution it is possible to obtain very high ventilation performance levels.

The vanes 14, moreover, can be provided integrally with the threaded ring 9 or be jointly associated therewith by means of fixing elements, heat-sealed, glued or coupled by means of mechanical joints.

The disk-like element 2 can have different shapes and dimensions; in the embodiment of the invention shown in the figures, for example, the grinding wheel 1 is of the depressed-center type, i.e., it has a concavity at the central portion of the second face 8, and the threaded ring 9 is arranged so as to be substantially recessed within said concave central portion. In this embodiment the thickness of the disk-like element 2 is such as to allow accommodation inside the through hole 5 of the cylindrical portion 16 of the threaded ring 9.

However, the disk-like element 2 might also be substantially flat and the threaded ring 9 might be arranged so as to protrude with respect to the second face 8.

In some cases (cutting discs) the thickness of the grinding wheel 1 might be particularly limited and might not make it possible to accommodate inside the central threaded hole 12 all of the cylindrical portion 16.

In FIGS. 14 a and 14 b the threaded ring 9 comprises at least one cavity 17 at the surface thereof affected by the annular portion 10 and arranged around the central threaded hole 12, so as to accommodate the centering rim of the supporting flange 7 of the rotating shaft 4 for the self-centering of the grinding wheel 1 with respect to the rotation axis of said rotating shaft.

The threaded ring 9, shown for example in FIGS. 3 to 13 and 15, moreover comprises at least one annular flange 18, which is substantially continuous and coaxial with the threaded ring 9 for connecting said vanes, the external radius of which is substantially equal to the distance between the second end 14 b of each vane 14 and the central rotation axis of the threaded ring 9 and the inside diameter is substantially larger than the diameter of the central threaded hole 12.

In the preferred embodiment, shown in FIGS. 13 a and 13 b, the annular ring 18 has at least a reduced radial thickness, i.e., the difference between the external radius and the internal radius thereof is substantially equal to 1 mm.

In this embodiment, moreover, the annular ring 18 is associated with the second ends 14 b of the vanes 14 on the same side where the first ends 14 a are associated with the threaded ring 9.

The annular ring 18 shaped like a thin ring or polygon of very limited cross-section and having an aerodynamic shape so as not to interfere with the air flow makes it possible to eliminate the possibility that these ventilating inserts might become mutually interlocked in the lines of the vibrating feeders used to transport them, which would prevent a normal and easy flow thereof.

In a further embodiment, illustrated in FIGS. 3 to 12 and in FIG. 15, the annular flange 18 is jointly associated with the second ends 14 b of the vanes 14 on the side opposite the threaded ring 9.

The threaded ring 9 furthermore comprises outflow openings 19 for the cooling fluid, which are interposed between the threaded ring 9 and the annular flange 18 at the outer perimetric rim 15 of the threaded ring 9, i.e., in the peripheral region of such threaded ring, in the region of interposition between the vanes 14.

The annular flange 18, in this case, makes it possible to channel in an optimized manner the cooling fluid inside the region occupied by the vanes 14 and therefore improve the inflow in an axial direction of the air and consequently the outflow in a radial direction thereof.

FIGS. 7 and 6 illustrate some variations of the flange 18 where said flange is bent respectively toward the grinding wheel 1 or outward depending on where one intends to direct the cooling flow.

In one embodiment, not shown in the figures, of the grinding wheel 1 the annular flange 18, for example, may have a substantially planar portion adapted to be arranged in contact with a corresponding planar surface provided on the disk-like element 2 and therefore be substantially covered by it.

In a further possible embodiment of the grinding wheel 1, such grinding wheel may comprise a plurality of through openings provided in the disk-like element 2 at the substantially central portion thereof for the outflow of the cooling fluid, propelled by the deflecting means during the rotary actuation of said grinding wheel, at the first face 6 of such disk-like element.

In a further possible embodiment of the grinding wheel 1 shown in FIGS. 8 and 9, the ventilating insert no longer has a perforated and threaded cylindrical central part but a thin central part that can be sandwiched and fastened between the grinding wheel 1 and a fastening flange 20 of the traditional type.

The vanes jointly connected to this thin part protrude in a substantially radial direction and can be surmounted or not by the annular flange 18. In this case there are no constraints for the type of thread, because it is possible to use the fastening flange 20 that the sanding machine usually has.

The threaded ring 9 shown in FIGS. 8 and 9 can be free or fixed, for example by adhesive bonding to the disk-like element 2.

In a further possible embodiment of the grinding wheel 1 shown in FIGS. 2 b, 12 b, 13 b, the ventilating vanes do not have a spiral arrangement but are straight. This solution is easier to provide in practice.

In a further possible embodiment of the grinding wheel 1 shown in FIGS. 16 a and 16 b, the vanes 14 are no longer cylindrical (i.e., they do not extend vertically in a direction that is parallel to the rotation axis of the grinding wheel 1) but oblique. This solution, although complex to provide in practice, approaches more closely the geometry of centrifugal compressors and can increase the ventilating effect. The inclined position of the vane 14 in fact improves the angle of attack of the cooling fluid that enters in an axial direction the ventilating insert and is propelled by it in a radial direction. In this case also, the insert can be provided with an annular ring 18 or not for channeling the fluid into the more peripheral region of such insert.

The ventilating insert may occupy all the concavity of such depressed-center grinding wheels because the higher the vanes 14 are, and therefore the more the depression is utilized, the higher the efficiency of the ventilation. For this purpose the vanes 14 might also protrude from the side of the grinding wheel 1 by a few millimeters and anyway always with the limitation of not causing problems of contact with the workpieces when one works with the grinding wheel slightly inclined or almost flat.

The vanes may have the most convenient desired height.

In depressed-center grinding wheels 1 that have deeper concavities, the problem of making the vanes protrude from the side of the grinding wheel does not exist, since the cavity is more than deep enough to provide vanes 14 of sufficient height.

The vanes 14, furthermore, might be available in a desired number, from a minimum of 2 until the desired efficiency is reached. Their thickness is also as desired and they may be oriented radially as well as deflected in any shape of the curvilinear type in a left-handed or right-handed direction. They may be straight or inclined, with a constant or variable inclination, by any angle.

Their outside diameter may be of any size, limited only by the necessity of not interfering with the article to be worked. These inserts may be also be applied on flat grinding wheels, where obviously the ventilating insert must protrude from the side of the grinding wheel. The ventilating insert on the flat grinding wheel might moreover be mounted on both sides of the grinding wheel if necessary.

These ventilating inserts may be made of plastic materials or of metallic materials. They may be applied to the grinding wheel both by adhesive bonding and by die-casting or injection molding on the grinding wheel itself. They may be pre-threaded at the center or threaded after being mounted or even not threaded at all.

In practice it has been found that the described invention achieves the intended aim and objects and in particular the fact is stressed that the ventilating insert, according to the invention, allows reducing the wear of the abrasive tool and thus increasing the performance and the average service life of said grinding wheels (or lamellar discs or fiber discs or Scotch-Brite® discs).

Moreover, the grinding wheel according to the invention, provided thus with a ventilating insert, allows working pieces without damaging their aesthetic finish or altering their physical and chemical characteristics.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

All the details may furthermore be replaced with other technically equivalent elements.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements without thereby abandoning the protective scope of the appended claims.

The disclosures in Italian Patent Application No. MO2010A000053 from which this application claims priority are incorporated herein by reference. 

1. A ventilating insert for substantially coaxial fixing of abrasive tools, such as deburring wheels, cutting wheels, fiber discs, Scotch-Brite® discs or tools, having an abrasive disk-shaped element, to a free end of a rotating shaft of a grinder, comprising: at least one threaded ring that comprises a central threaded hole for coupling with corresponding threaded means provided on a free end of a rotating shaft, said threaded ring having an annular portion which is jointly associatable with the disk-shaped element, arranged substantially coaxially thereto; and deflecting means for deflecting at least one fluid for cooling the disk-shaped element which are associated with said threaded ring for propelling radially the cooling fluid from a central region to a peripheral region of the disk-shaped element during rotation thereof.
 2. The insert of claim 1, wherein said deflecting means comprise a plurality of vanes that protrude substantially radially and diverge with respect to each other, at least one first end of said vanes being jointly associated with said threaded ring.
 3. The insert of claim 2, wherein each one of said vanes comprises a substantially rectilinear longitudinal extension which protrudes radially with respect to said threaded ring.
 4. The insert of claim 2, wherein each one of said vanes comprises a substantially C-shaped curved longitudinal extension which forms a deflector of the flow of said cooling fluid.
 5. The insert of claim 2, wherein said threaded ring comprises a substantially cup-shaped portion, which surrounds said central threaded hole and is arranged opposite said annular portion, said vanes being formed at said substantially cup-shaped portion.
 6. The insert of claim 2, wherein a second end of each one of said vanes is provided so that it substantially cantilevers out with respect to said threaded ring.
 7. The insert of claim 6, wherein at least one annular flange which is substantially continuous and coaxial with said threaded ring, for connecting said vanes, whose outside radius is substantially equal to a distance between the second ends of said vanes and a rotation axis of said threaded ring, and whose inside diameter is substantially larger than said central threaded hole, said annular flange being jointly associated with said second ends of said vanes.
 8. The insert of claim 7, wherein a connecting surface between each pair of contiguous ones of said vanes, provided in said threaded ring, has a substantially frustum-shaped generatrix in a proximal region, with a longitudinal axis that is substantially inclined with respect to the rotation axis of said threaded ring.
 9. The insert of claim 1, in combination with an abrasive tool having an abrasive disk-shaped element, wherein the disk-shaped element comprises through openings provided at a substantially central portion thereof for outflow of the cooling fluid at a back part of the disk-like element. 